Michael Heidelberger as a Carbohydrate Chemist

The deoxyaldaric acids corresponding in structure to the 3-deoxy-2-C-(hydroxymethyl)aldonic (isosaccharinic) acids have been identified as products of treatment of various carbohydrates with alkali and oxygen-alkali. The structures of the acids were determined from the mass spectra of their Me₃Si derivatives on the basis of previously known, specific fragmentation reactions. The g.l.c.-m.s. technique was used, and g.l.c. retention data are given. The identified species are 2-deoxy-3-C-(hydroxymethyl)tetraric, 3-deoxy-2-C-hydroxymethyl-erythro-pentaric, 3-deoxy-2-C-hydroxymethyl-threo-pentaric, 2-methyltartronic, 2-(2-hydroxyethyl)tartronic, and 2-(2,3-dihydroxypropyl)tartronic acids. Their formation from 4-O-substituted uronic and ulosonic acids is briefly discussed.     

Dynamic gene amplification and function diversification of grass-specific O-methyltransferase gene family

The plant O-methyltransferases are dependent on S-Adenosyl-l-methionine, which can catalyze a variety of secondary metabolites. Here we identified different number of OMT genes from the respective grass genomes. Phylogenetic analysis showed that this OMT gene family is a grass-specific gene family that is different from COMT. Most of genes were expanded by tandem and segment duplication after the species split from their progenitor. Furthermore, genes from Group I and two clusters from group II are only present in Panicoideae, which included Bx10 and Bx7 involved in the benzoxazinoids pathway, suggesting these genes could participate in insect resistance in Panicoideae. Gene expression profiles showed that OMT genes were preferentially expressed in vegetative stages, especially in roots. These results revealed that this grass-specific OMT gene family could affect the development of vegetative stages, and be involved in the benzoxazinoids pathway or suberin biosynthesis that was different from COMT.     

The Smad3-miR-29b/miR-29c axis mediates the protective effect of macrophage migration inhibitory factor against cardiac fibrosis

Although macrophage migration inhibitory factor (MIF) is known to have antioxidant property, the role of MIF in cardiac fibrosis has not been well understood. We found that MIF was markedly increased in angiotension II (Ang-II)-infused mouse myocardium. Myocardial function was impaired and cardiac fibrosis was aggravated in Mif-knockout (Mif-KO) mice. Functionally, overexpression of MIF and MIF protein could inhibit the expression of fibrosis-associated collagen (Col) 1a1, COL3A1 and α-SMA, and Smad3 activation in mouse cardiac fibroblasts (CFs). Consistently, MIF deficiency could exacerbate the expression of COL1A1, COL3A1 and α-SMA, and Smad3 activation in Ang-II-treated CFs. Interestingly, microRNA-29b-3p (miR-29b-3p) and microRNA-29c-3p (miR-29c-3p) were down-regulated in the myocardium of Ang-II-infused Mif-KO mice but upregulated in CFs with MIF overexpression or by treatment with MIF protein. MiR-29b-3p and miR-29c-3p could suppress the expression of COL1A1, COL3A1 and α-SMA in CFs through targeting the pro-fibrosis genes of transforming growth factor beta-2 (Tgfb2) and matrix metallopeptidase 2 (Mmp2). We further demonstrated that Mif inhibited reactive oxygen species (ROS) generation and Smad3 activation, and rescued the decrease of miR-29b-3p and miR-29c-3p in Ang-II-treated CFs. Smad3 inhibitors, SIS3 and Naringenin, and Smad3 siRNA could reverse the decrease of miR-29b-3p and miR-29c-3p in Ang-II-treated CFs. Taken together, our data demonstrated that the Smad3-miR-29b/miR-29c axis mediates the inhibitory effect of macrophage migration inhibitory factor on cardiac fibrosis.     

Highly diverse cembranoids from the South China Sea soft coral Sinularia scabra as a new class of potential immunosuppressive agents

The first and in-depth chemical investigation of the South China Sea soft coral Sinularia scabra has resulted to the isolation of a library of diverse cembrane type diterpenoids, including six new compounds, namely xiguscabrates A and B (1 and 2), xiguscabral A (3), xiguscabrols A and B (4 and 5), and 8-epi-xiguscabrol B (6), and twenty-seven known analogs (7–33). Their structures were elucidated by extensive spectroscopic analysis and by the comparison with literature data. In bioassay, several isolates exhibited inhibitory effects on the ConA-induced T lymphocytes and/or LPS-induced B lymphocytes proliferation. Among them, compound 24 showed considerable specific inhibition on B cell proliferation, with IC₅₀ value of 4.4 μM and selectivity index (SI) of 10.9. The structure-activity relationship (SAR) of the tested metabolites was analyzed, and the further mechanism study of the specific B-cell targeted immunosuppressive compound 24 on purified CD19⁺ B cells was also performed to uncover the effects on the function and maturity of B cells, including cytokines production, abnormal activation, antigen presenting capacity and plasma cells formation.     

Size and heterogeneity rather than landscape context determine plant species richness in semi‐natural grasslands

Question: Is plant diversity in fragmented semi‐natural grasslands related to present and historical landscape context? Location: Southern Sweden. Methods: Plant diversity was described at 30 semi‐natural grassland sites in terms of total and specialist plant species richness at the site and species density at different scales (0.5–10 m²). These measures are commonly used to assess conservation value of semi‐natural grasslands. Landscape context was measured as contemporary connectivity to other semi‐natural grasslands, historical connectivity 50 years ago, amount of linear elements potentially suitable for dispersal (road verges, power line clearings), and amount of forest (inverse of the openness of the landscape). Results: The diversity measures were generally correlated with each other, implying that species richness in a subset of the grassland can predict the total richness. Plant species density at three scales (0.5 m², 10 m² and total) was related to the landscape context using an information theoretic approach. Results showed that total species richness increased with increased size of grasslands, contrary to earlier diversity studies in semi‐natural grasslands. Larger grasslands were more heterogeneous than smaller grasslands, and this is a likely reason for the species‐area relationship. Heterogeneity was also of high importance at the smaller scales (0.5 m², 10 m²). With increased amount of forest, total species richness increased but species density on 10 m² decreased. There was no influence of connectivity in either the contemporary or the historical landscape, contrary to previous studies. Conclusions: Grassland size and heterogeneity are of greater importance for plant diversity in semi‐natural grassland, than grassland connectivity in the landscape.     

Perturbation at the sea floor during the Paleocene–Eocene Thermal Maximum: Evidence from benthic foraminifera at Contessa Road, Italy

Detailed analyses of the benthic foraminiferal assemblages extracted with the cold acetolyse method together with high resolution geochemical and mineralogical investigations across the Paleocene/Eocene (P/E) boundary of the classical succession at Contessa Road (western Tethys), allowed to recognize and document the Paleocene–Eocene Thermal Maximum (PETM) interval, the position of the Benthic Extinction Event (BEE) and the early recovery of benthic faunas in the aftermath of benthic foraminiferal extinction. The stratigraphical interval spanning the P/E boundary consists of dominantly pelagic limestones and two prominent marly beds. Benthic foraminifera indicate that these sediments were deposited at lower bathyal depth, not deeper than 1000–1500 m. The Carbon Isotope Excursion (CIE) interval is characterized by high barite abundance with a peak at the base of the same stratigraphic interval, indicating a complete, although condensed record of the early CIE. A succession of events and changes in the taxonomic structure of benthic foraminifera has been recognized that may be of use for supra-regional stratigraphic correlation across the P/E boundary interval. The composition of the benthic foraminiferal assemblages, dominated by infaunal taxa, indicates mesotrophic and changing conditions on the sea floor during the last  45 kyr of the Paleocene. The BEE occurs at the base of the CIE within the lower marly bed and it is recorded by the extinction of several deep-water cosmopolitan taxa. Then, the lysocline/CCD rose and severe carbonate dissolution occurred. Preservation deteriorated, the faunal density and simple diversity dropped to minimum values and a peak of Glomospira spp. has been observed. Stress-tolerant and opportunistic groups, represented mainly by bi-and triserial taxa, dominate the low-diversity post-extinction assemblages, indicating a benthic foraminiferal recovery under environmental unstable conditions, probably within a context of sustained food transfer to the bottom. A three-phase pattern of faunal recovery is recognizable. At first the lysocline/CCD started to descend and then recovered. Small-sized “Bulimina”, Oridorsalis umbonatus, and Tappanina selmensis rapidly repopulated the severely stressed environment. Later on, Siphogenerinoides brevispinosa massively returns, dominating the assemblage together with other buliminids, Nuttallides truempyi, and Anomalinoides sp.1. Finally, a marked drop in abundance of S. brevispinosa is followed by a bloom of the opportunistic and recolonizer agglutinated Pseudobolivina that, for the first time, is recorded within the main CIE. A second interval of dissolution, but less severe than the previous one, has been recognized within the upper marly bed (uppermost part of the main CIE interval) and it is interpreted as a renewed, less pronounced shoaling of the lysocline/CCD that interrupted the recovery of benthic faunas. This further rise likely represents a response to persistent instability of ocean geochemistry in this sector of the Tethys before the end of the CIE. In the CIE recovery and post CIE intervals, the composition of the benthic foraminiferal assemblages suggests mesotrophic and unstable conditions at the sea floor. According to the geochemical proxy for redox conditions, the deposition of the PETM sediments at Contessa Road occurred in well-oxygenated waters, leading out a widespread oxygen depletion as major cause of the BEE. Changing oceanic productivity, carbonate corrosivity and global warming appear to have played a much more important role in the major benthic foraminiferal extinction at the P/E boundary.     

Fire and resprouting in Mediterranean ecosystems: insights from an external biogeographical region, the mexical shrubland

We investigated modes of regeneration of dominant species of the mexical vegetation after fire. The mexical shrubland shows a remarkable structural, morphological, and floristic similarity to Mediterranean-type vegetation and is considered a relict of the Madro-Tertiary Geoflora under a non-Mediterranean climate. This vegetation provides an ideal scenario to test the role of fire in Mediterranean ecosystems because historical fire occurrence is absent and the species assembly is constituted mostly by Madro-Tertiary elements and Neotropical species (some of them, endemic species from Mexico). The existence of congeneric species of the California chaparral allows us to determine the regeneration ability of these communities after fire in relation to resprouting and seeding strategies, which are widespread modes reported in the Mediterranean-type vegetation. By the experimental application of fire in the two biogeographical groups of species, we tested the hypothesis that low resprouting ability of California congeneric species (Madro-Tertiary species) after fire would indicate that fire has played an important selective force in the resprouting habit. A low resprouting ability in the Neotropical group of species would suggest that fire has molded the set of species dominating fire-prone environments.Our results indicated that resprouting is a widespread trait in the mexical species characterized by the presence of lignotubers and burls. Resprouting can be considered an ancient trait, probably linked to losses of aboveground biomass, that became a pre-adaptation in Mediterranean fire-prone communities. The Neotropical group of species showed less ability to regenerate after fire, and small plants were more likely to die after disturbance in this group than in the Madro-Tertiary group. The resprouting feature and the seeder strategy of other species after a fire in the mexical shrubland are similar to Mediterranean-type ecosystems, emphasizing their common origin and the relevance of phylogenetic and biogeographical studies to explain current patterns of vegetation.